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rcu: Move quiescent-state forcing into kthread

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As the first step towards allowing quiescent-state forcing to be
preemptible, this commit moves RCU quiescent-state forcing into the
same kthread that is now used to initialize and clean up after grace
periods.  This is yet another step towards keeping scheduling
latency down to a dull roar.

Updated to change from raw_spin_lock_irqsave() to raw_spin_lock_irq()
and to remove the now-unused rcu_state structure fields as suggested by
Peter Zijlstra.

Reported-by: Mike Galbraith <mgalbraith@suse.de>
Reported-by: Dimitri Sivanich <sivanich@sgi.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This commit is contained in:
Paul E. McKenney
2012-06-22 17:06:26 -07:00
parent b402b73b3a
commit 4cdfc175c2
3 changed files with 82 additions and 138 deletions
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13
kernel/rcutree.h
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@@ -378,13 +378,6 @@ struct rcu_state {
u8 fqs_state ____cacheline_internodealigned_in_smp;
/* Force QS state. */
u8 fqs_active; /* force_quiescent_state() */
/* is running. */
u8 fqs_need_gp; /* A CPU was prevented from */
/* starting a new grace */
/* period because */
/* force_quiescent_state() */
/* was running. */
u8 boost; /* Subject to priority boost. */
unsigned long gpnum; /* Current gp number. */
unsigned long completed; /* # of last completed gp. */
@@ -413,8 +406,6 @@ struct rcu_state {
struct completion barrier_completion; /* Wake at barrier end. */
unsigned long n_barrier_done; /* ++ at start and end of */
/* _rcu_barrier(). */
raw_spinlock_t fqslock; /* Only one task forcing */
/* quiescent states. */
unsigned long jiffies_force_qs; /* Time at which to invoke */
/* force_quiescent_state(). */
unsigned long n_force_qs; /* Number of calls to */
@@ -433,6 +424,10 @@ struct rcu_state {
struct list_head flavors; /* List of RCU flavors. */
};
/* Values for rcu_state structure's gp_flags field. */
#define RCU_GP_FLAG_INIT 0x1 /* Need grace-period initialization. */
#define RCU_GP_FLAG_FQS 0x2 /* Need grace-period quiescent-state forcing. */
extern struct list_head rcu_struct_flavors;
#define for_each_rcu_flavor(rsp) \
list_for_each_entry((rsp), &rcu_struct_flavors, flavors)